The disclosure of Japanese Patent Application No. 2000-254470 filed on Aug. 24, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an activation control apparatus and method of an airbag apparatus and, more particularly, to an airbag apparatus activation control apparatus and method that is suitable in properly activating an airbag apparatus for protecting an occupant at the time of a collision a vehicle.
2. Description of the Related Art
An activation control apparatus of an airbag apparatus is conventionally known which has a floor sensor that is disposed in a floor tunnel of a vehicle body and that outputs a signal corresponding to the impact that occurs on the floor tunnel, and which deploys an airbag when the value of a parameter based on the output signal of the floor sensor exceeds a threshold, as disclosed in, for example, Japanese Patent Application Laid-Open No. HEI 11-286257. This apparatus further has a satellite sensor that is disposed in a forward portion of the vehicle body and that outputs a signal corresponding to the impact received by the forward portion of the vehicle body. The apparatus increases the amount of reduction of the aforementioned threshold with increases in the impact received by the forward portion of the vehicle body that is detected based on the output signal of the satellite sensor. Therefore, the airbag is deployed more easily if the impact that occurs on the forward portion of the vehicle body is greater. Thus, according to the above-described conventional apparatus, the airbag apparatus for protecting an occupant can be appropriately activated.
In the above-described conventional apparatus, the threshold for deploying the airbag is reduced by a greater amount if the impact given to the forward portion of the vehicle body that is detected based on the output signal of a satellite sensor is greater. In some cases, noises are superimposed on the output signal of the satellite sensor. If in such a case, it is determined that the impact given to the forward portion of the vehicle body is great, and therefore the threshold is immediately reduced, and the airbag becomes prone to be deployed. Thus, there arises a danger of inadvertent deployment of the airbag. Therefore, in view of proper deployment of the airbag, it is not appropriate to immediately reduce the threshold to a value corresponding to the output signal of a satellite sensor if the output signal of the satellite sensor fluctuates merely for a short period. However, in the above-described conventional apparatus, no consideration is given with regard to a technique of switching values of the threshold for deployment of the airbag.
It is an object of the invention to provide an airbag apparatus activation control apparatus and method capable of properly activating an airbag apparatus even if a noise is superimposed on the output signal of a sensor for use for setting a threshold value for activation of the airbag apparatus.
A first aspect of the invention is an activation control apparatus of an airbag apparatus including a first sensor that is disposed at a predetermined position in a vehicle body and that outputs a signal corresponding to an impact that occurs on a vehicle, activation control means for activating the airbag apparatus if a parameter based on the signal outputted by the first sensor exceeds a predetermined threshold, a second sensor that is disposed forward of the predetermined position of the first sensor within the vehicle body and that outputs a signal corresponding to an impact that occurs on the vehicle, and threshold setting means for setting one value of at least three values as the predetermined threshold based on the signal outputted by the second sensor. The activation control apparatus further includes threshold switching means for, if while the one value of the at least three values has been set as the predetermined threshold by the threshold setting means, another value is to be set as the predetermined threshold, switching the predetermined threshold to the another value after a state where the another value is to be set as the predetermined threshold continues for a time corresponding to a difference between the one value and the another value.
According to the above-described first aspect, if one value has been set as a predetermined threshold for activation of the airbag apparatus, the predetermined threshold is switched to as the predetermined threshold after the state where the another value is to be set continues for a time corresponding to a difference between the one value and the another value. Therefore, under a circumstance where the predetermined threshold can considerably change due to noises being superimposed on the output signal of the second sensor, an event that the airbag apparatus suddenly becomes prone to be activated or suddenly becomes less prone to be activated is avoided. Hence, according to the invention, it becomes possible to substantially prevent inadvertent activation of the airbag apparatus even in a case where noises are superimposed on the output signal of the second sensor. Thus, the airbag apparatus can be properly activated.
A second aspect of the invention is an activation control apparatus of an airbag apparatus including a first sensor that is disposed at a predetermined position in a vehicle body and that outputs a signal corresponding to an impact that occurs on a vehicle, activation control means for activating the airbag apparatus if a parameter based on the signal outputted by the first sensor exceeds a predetermined threshold changing pattern, a second sensor that is disposed forward of the predetermined position of the first sensor within the vehicle body and that outputs a signal corresponding to an impact that occurs on the vehicle, and threshold changing pattern setting means for setting one changing pattern of at least three changing patterns as the predetermined threshold changing pattern based on the signal outputted by the second sensor. The activation control apparatus further includes threshold changing pattern switching means for, if while the one changing pattern of the at least three changing patterns has been set as the predetermined threshold changing pattern by the threshold changing pattern setting means, another changing pattern is to be set as the predetermined threshold changing pattern, switching the predetermined threshold changing pattern to the another changing pattern after a state where the another changing pattern is to be set as the predetermined threshold changing pattern continues for a time corresponding to a difference between the one changing pattern and the another changing pattern.
According to the second aspect, if while one changing pattern has been set as a predetermined threshold changing pattern, another changing pattern is to be set as the predetermined threshold changing pattern, the predetermined threshold changing pattern is switched to the another changing pattern after the state where the another changing pattern is to be set continues for a time corresponding to a difference between the one changing pattern and the another changing pattern. Therefore, under a circumstance where the predetermined threshold changing pattern can considerably change due to noises being superimposed on the output signal of the second sensor, an event that the airbag apparatus suddenly becomes prone to be activated or suddenly becomes less prone to be activated is avoided. Hence, according to the invention, it becomes possible to substantially prevent inadvertent activation of the airbag apparatus even in a case where noises are superimposed on the output signal of the second sensor. Thus, the airbag apparatus can be properly activated.
If an arrangement is adopted in which the predetermined threshold is switched from one value only after the state where another value is to be set continues for the time corresponding to a difference between the one value and the another value, or in which the predetermined threshold is switched from one changing pattern only after the state where another changing pattern is to be set continues for the time corresponding to a difference between the one changing pattern and the another changing pattern, the responsiveness of the switching of the predetermined threshold or the predetermined threshold changing pattern deteriorates, so that an event that the airbag apparatus is not properly activated may occur.
In the first aspect, the threshold switching means may switch the predetermined threshold stepwise at every predetermined time during a process in which a time of continuation of the state where the another value is to be set as the predetermined threshold reaches the time corresponding to the difference between the one value and the another value.
In the second aspect, the threshold changing pattern switching means may switch the predetermined threshold changing pattern stepwise at every predetermined time during a process in which a time of continuation of the state where the another changing pattern is to be set as the predetermined threshold changing pattern reaches the time corresponding to the difference between the one changing pattern and the another changing pattern.
If during a process of switching the predetermined threshold or the predetermined threshold changing pattern for activation of the airbag apparatus via the threshold switching means or the threshold changing pattern switching means, a state where another value is to be set as the predetermined threshold or another changing pattern is to be set as the predetermined threshold changing pattern discontinues, there is no need to switch the predetermined threshold or the predetermined threshold changing pattern to the another value or the another changing pattern.
Therefore, in the first aspect, the activation control apparatus may further include threshold switching aborting means for aborting switching of the predetermined threshold to the another value if the state where the another value is to be set as the predetermined threshold discontinues before the predetermined threshold is switched to the another value by the threshold switching means.
Likewise, in the second aspect, the activation control apparatus may further include threshold changing pattern switching aborting means for aborting switching of the predetermined threshold changing pattern to the another changing pattern if the state where the another changing pattern is to be set as the predetermined threshold changing pattern discontinues before the predetermined threshold changing pattern is switched to the another changing pattern by the threshold changing pattern switching means.
If an impact on the vehicle ends within a short time, the duration of fluctuation of the output signal of the second sensor usually becomes short. If the output signal of the second sensor fluctuates only for a short period, it becomes impossible to switch the threshold or the threshold changing pattern for activation of the airbag apparatus to a desired value or a desired changing pattern provided that the impact on the vehicle is great. Therefore, in order to reliably switch the threshold or the threshold changing pattern to a desired value or a desired changing pattern even if an impact on a forward portion of the vehicle body discontinues within a short time, it is appropriate to sufficiently lengthen the duration during which the second sensor outputs a signal corresponding to the impact given to the vehicle if the impact on the forward portion of the vehicle body discontinues in a short time.
Therefore, in the first and second aspects, the second sensor may continue to output a signal for at least a predetermined time.